A V-belt continuously variable transmission is configured such that a V-belt is wrapped around a primary pulley on an input side and a secondary pulley on an output side so that transmission of rotation from a power source such as an engine and a motor can be performed.
In order to make shift possible, such a configuration is adopted that the primary pulley and the secondary pulley are respectively configured such that each movable sheave which is one of sheaves forming pulley V-shaped grooves can be stroked in axial directions toward the corresponding other fixed sheave.
In performing shift, stroke control is performed to the movable sheave of one pulley of these pulleys in an axial direction of coming close to or going away from a corresponding fixed sheave, while stroke control is performed to the movable sheave of the other pulley in the axial direction of going away from or of coming close to a corresponding fixed sheave, so that a pulley rotation ratio between both the pulleys is continuously changed toward a value corresponding to a target speed ratio, thereby shift is made.
In the control of shift, as described in JP62-273189A, a pulley rotation ratio corresponding to a torque amplifying ratio of the transmission required in a vehicle driving state (vehicle speed information or a power source load state) is defined as the target speed ratio (a target input rotation speed) from the vehicle driving state, so that continuous shift is performed such that the pulley rotation ratio coincides with the value corresponding to the target speed ratio (the target input rotation speed).
On the other hand, as the V-belt continuously variable transmission, there is conventionally a V-belt continuously variable transmission with a belt slip control apparatus which controls a belt slip ratio actively such that a slip ratio of the V-belt to one of the primary pulley and the secondary pulley reaches a proper value, as described in JP2006-511765A.